Sailing yacht with a centerboard

ABSTRACT

In a sailing yacht with a centerboard having a hull accommodating a centerboard well containing the centerboard capable of movement therein through rollers along curvilinear guides provided in the centerboard well, according to the invention, the rollers and guides are positioned at either side of the centerboard along its stern edge, the rollers being secured immediately on the centerboard.

BACKGROUND OF THE INVENTION

1. Description of the Related Art

The invention relates generally to shipbuilding, and more particularlyto sailing yachts having a centerboard.

2. Background of the Invention

There are known sailing yachts provided with a straight drop-keel orcenterboard.

Accommodated in the middle portion of the yacht hull is a rectangularcenterboard well receiving a substantially rectangular centerboardcapable of movement in the vertical plane. Sliding of the centerboardfrom the well is prevented by lock pins.

Substantial manual efforts are required for dropping or retracting thecenterboard whereas a system of tackles is required in the "Micro" orlarger class yachts. The sailing yachts having a drop-keel centerboardare usually so constructed that in the raised position the centerboardoccupies much space either in the cockpit or in the cabin. This in turnmakes such yachts less comfortable, another disadvantage of such yachtsbeing a rather low sailing performance, due to that the drop-keelcenterboards do not allow the yachts to head in the wind accompanied byan increase in the hydraulic resistance and reduction in the speed ofthe yacht.

There is also known a centerboard sailing yacht as described in U.S.Pat. No. 3,547,065. The straight centerboard is fashioned as aparallelogram with a system for raising and lowering the centerboardincluding guides inside the centerboard well with rollers on which thecenterboard moves.

Modification of the system for raising and lowering the centerboardsubstantially facilitates handling of the yacht, although fails to makethe yacht more comfortable. However, a principle disadvantage of such ayacht is low sailing performance accounted by the shape of thecenterboard making it impossible to control the center of sail, and thearrangement of the centerboard relative to the hull. Such structuraldisadvantages result in an increase in the hydraulic resistance, andconsequently in a loss of speed as the yacht heads in the wind.

Attempts to partially obviate the heretofore mentioned disadvantages areknown from the same patent U.S. Pat. No. 3,547,065. The sailing yachtdescribed herein comprises a hull the bow part of which accommodates acenterboard well. Provided inside the well are curvilinear guides, andthe centerboard moves on rollers. This centerboard easily moves alongthe guides, whereas its shape and arrangement make the yacht morecomfortable by placing the centerboard out of the cabin or cockpit. Inaddition, the curvilinear shape of the centerboard makes it possible tocontrol the center of lateral resistance of the yacht by changing theposition of the geometrical center.

However, while solving partially the known problems, the prototypefeatures such disadvantages as low sailing performance of the yacht.This centerboard construction makes it possible to prevent deviation ofthe centerboard in the longitudinal centerplane of the yacht whichleads, as the yacht heads in the wind, to an increase in the hydraulicresistance and loss of speed. In order to control the center of lateralresistance, the curvilinear guides are such that the height of thecenterboard well is greater, affecting the space of the cabin, whichmakes the cabin less comfortable for the crew. Notwithstanding the factthat such a centerboard construction affords to control the center oflateral resistance, the range of such control is negligeable. Therewith,a change in the lateral resistance of the yacht attainable throughretracting the centerboard in the well results in reduced useful surfaceand consequently in diminishing the principle function thereof, viz.,provision of the lateral resistance. It is also to be noted that thisconstruction of the centerboard overcomplicates assembly and repairoperations, since the centerboard can be inserted to or removed from thewell only through the well outlet at the bottom of the yacht.

SUMMARY OF THE INVENTION

The present invention is directed toward the provision of a sailingyacht having such a construction of the centerboard as to improve thesailing performance through reducing the hydraulic resistance of theyacht as it moves in the wind and controlling the center of lateralresistance within a wide range, while maintaining the useful centerboardarea, making the cabin or cockpit more comfortable for the crew, andsimplifying assembly and repair operations.

The aims of providing a sailing yacht with a centerboard capable ofimproving its sailing performance is attained by a sailing yacht thehull of which accommodates a well with a centerboard capable of movementtherein on rollers along curvilinear guides provided in the well.According to the invention, the rollers and guides are positioned atboth sides of the centerboard along its stern edge, the roller beingsecured directly on the centerboard.

Such and arrangement allows the centerboard to deviate from thelongitudinal centerplane during sharp courses, thereby reducing thehydraulic resistance and allowing a higher speed. Improvement in thesailing performance is attained due to that the angle of attack isincreased in response to deviation of the centerboard in plan in apreset direction to an angle to 2-3°.

Such a deviation takes place automatically under the action of theincident flow of water, as the yacht heads windwards with an inevitabledrift. After tacking the incoming flow of water causes the centerboardto swing to the opposite side by turning relative to the line connectingthe rollers mounted at the stern edge.

The centerboard can be constructed so that the shape of its bow edgecorresponds to the shape of the keel line of the hull under thecenterboard well, whereas the stern edge and longitudinal axis of theguides have the shape of arcs of concentric circles.

This construction enables considerable reduction in the height of thecenterboard well through a more complete utilization of its interior toresult in more headroom in the cabin thereby making the yacht morecomfortable.

Preferably, the stern edge of the centerboard has the shape of an arc ofa circle having a radius: ##EQU1## R_(d) is the radius of curvature ofthe stern edge of the centerboard; and

L_(wL) is the length of the hull along the waterline.

Such an arrangement attains the optimum relationship between thedimensions of the centerboard, centerboard well, and cabin.

Alternatively, the longitudinal axis of each guide has the shape of twointerconnected arcs of circles with centers thereof resting at one sideof the longitudinal axis, the radius of the arc nearest the outlet fromthe centerboard well being smaller than the radius of the other arc.

This arrangement of the guides allows the centerboard to vary thelateral resistance within a wide range. Displacement of the center oflateral resistance of the centerboard bowise relative to the center ofsail pressure results in a larger surface area of the centerboard, andconsequently in reduce yacht drift.

Preferably, the curvilinear guides are U-shaped, the upper shelf of theguides having recesses to ensure the passage of the rollerstherethrough.

This shape of the guides ensures more convenient assembly operations.The centerboard can be therefore installed through the cabin withoutresorting to keel-blocking.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other advantages of the present invention will become morefully apparent from a more detailed description that follows withreference to the accompanying drawings, in which:

FIG. 1 is a side partially cut-away view of the proposed yacht having acenterboard;

FIG. 2 is an enlarged cross section of a centerboard well;

FIG. 3 is an alternative modification of a curvilinear guide with arecess in the upper shelf thereof;

FIG. 4 is a centerboard well in which curvilinear guides are curved inthe form of two interconnected arcs of a circle of different radii;

FIG. 5 is a plan view of the centerboard; and

FIG. 6 is a schematic representation of the position of the center ofsail pressure in response to variations in the position of the center oflateral resistance of the centerboard.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The proposed centerboard sailing yacht comprises a hull I (FIG. 1), adeck 2, and rigging 3. Arranged inside the hull I is a centerboard well4 having curvilinear guides 5 at both sides of the centerboard 6, whichincludes a stern edge 7 and a bow edge 8. The guides 5 extend along thestern edge 7 of the centerboard consisting of two parts (FIGS. 1 and 2):a tear-shaped submerged part 9, and non-streamlined part 10 alwaysresting inside the well 4 and rollers 11 arranged in paris at the sidesof the stern edge. The most preferable arrangement of the rollers is atthe top of the nonstreamlined part thereof. The number of rollers to beemployed depends on the size of the centerboard, and is determined fromthe present angle of inclination relative to the longitudinalcenterplane. Arrangement of the rollers at the top of the centerboard ispreferable because it allows suspension of the centerboard on the guides5 for the centerboard to be capable of deviating, relative to thelongitudinal centerplane, by a certain angle (FIG. 3), such as 2-3°(optimum for the "Micro" class yachts). The guides 5 of the centerboardare U-shaped, and an upper shelf 12 thereof has recesses 13 (FIG. 4) toallow the passage of rollers 11 therethrough. The upper shelves 12 ofthe guides 5 are arranged at one level and have equal curviture. Lowershelves 14 ensure suspension of the centerboard in the well and movementthereof along the guides. The yacht comprises a means 15 for lifting andlowering the centerboard 6 having the form of two ropes 16 (FIG. 5). Thecenterboard well 4 has a cover 17 at the top, and an elastic spacer 18at the bottom. The centerboard has a ballasting hole 19 through whichthe interior of the centerboard is filled with water. The stern edge ofthe centerboard is shaped as an arc of a circle having a radiusdetermined from: ##EQU2## R_(d) is the radius of curvature of the sternedge of the centerboard; and

L_(wL) is the length of the hull along the waterline.

The shape of curvature of the guides is dictated by the size of theyacht and its designation (e.g., a racing yacht, or a pleasure yacht).Particularly, in the proposed embodiment a longitudinal axis 20 (FIG. 5)of the guides 21 can have the shape of two interconnected arcs ofcircles "R" and "r" with centers thereof resting at one side of thelongitudinal axis, the radius "r" of the arc closest to the outlet fromthe centerboard well 4 being smaller than the radius "R" of the otherarc.

The sailing yacht having a centerboard according to the invention isoperated as follows.

In a fair wind, when the centerboard is completely retracted in the well4, its center of gravity is below the geometrical center, which ensuresstable position thereof inside the well (FIG. 1). Such a position of thecenterboard prevents inadvertent dropping thereof form the well, anddoes not require a special system for locking the centerboard in theextreme working and non-working positions.

When the wind changes, and the drift force is great relative to theforce which moves the yacht forward, it is necessary to provide asubstantial lateral resistance. With this aim in view and depending onthe course of the yacht, the centerboard is lowered to a required depth.As the centerboard is lowered, the interior of the centerboard is filledwith water through the hole 19. Raising and lowering the centerboard isexecuted by a system of ropes 16 handled from the cockpit (not shown).

For carrying out preventive maintenance the cover 17 of the centerboardwell 4 is swung back, the rollers 11 are registered with the recesses13, and the centerboard is removed from the well. Mounting thecenterboard inside the well during assembly is done in the followingmanner. The centerboard is lowered between the guides so that therollers 11 could enter the recesses 13 and bear on the lower shelves 14of the centerboard guides. The thus facilitated assembly has been madepossible thanks to structural modifications of the yacht, whichsimplifies preventive maintenance and repair operations. For the yachtto retain a given straight movement it is necessary to continuouslyalign the center of lateral resistance with the center of sail pressure(FIG. 6). Assuming that the yacht heads on a set course, the center ofsail pressure and the center of lateral resistance of the centerboardrest along one line at points B and B', respectively. (FIG. 6). If thecenter of sail pressure moves to point C and the centerboard remains inthe same position, a swinging moment occurs. In this case for the yachtto retain the present course it is necessary to align the center oflateral resistance of the centerboard with the center of sail pressuresuch that they again lie in one line. For this purpose the centerboardis lowered from the well so that the center of lateral resistancethereof would be at point C'. This is accompanied by an increase in theuseful surface area of the centerboard. Conversely, when the center ofsail pressure moves to point A, the centerboard should be retracted inthe well so that its center of lateral resistance could displace topoint A'.

The proposed centerboard arrangement can be used for yachts of anydimensions. The invention allows to improve the sailing performance ofthe yacht through reducing the hydraulic resistance of the yacht as itmoves in the wind, and expand the range of adjustment to improve thesteerability of the yacht. Another advantage is improved performance andmore comfortable conditions on board, since the proposed technicalsolution allows retraction the centerboard to a well of a substantiallyreduced height, the position of the well inside the hull allowing amaximum use of the interior volume of the yacht, as well as facilitatingassembly and repair operations by making it possible to install thecenterboard from the inside of the cabin, rather than from the yachtbottom, thus obviating the need for keel-blocking the yacht.

We claim:
 1. A sailing yacht with a centerboard comprising a hullaccommodating a centerboard well containing the centerboard capable ofmovement therein through rollers along curvilinear shaped guides,wherein the rollers and horizontal shelves of the guides are positionedat both sides of the centerboard along its stern edge, the rollers beingsecured on lateral surfaces of the centerboard at the stern edge of itsnon-immersible portion to rest on horizontal shelves of the guides.
 2. Asailing yacht as claimed in claim 1, wherein the shape of a bow edge ofthe centerboard corresponds to the shape of a keel line of the hullunder the centerboard well, whereas the stern edge and longitudinal axisof the guides have the shape of arcs of concentric circles.
 3. A sailingyacht as claimed in claim 2, wherein the stern edge of the centerboardhas the shape of an arc of a circle having a radius: ##EQU3## R_(d) isthe radius of curvature of the stern edge of the centerboard; andL_(wL)is the length of the hull along the waterline.
 4. A sailing yacht asclaimed in claim 1, wherein the longitudinal axis of each guide has theshape of two interconnected arcs of circles with centers thereof restingat one side of the longitudinal axis, whereas the radius of the arcnearest to an outlet from the centerboard well is less than the radiusof the other arc.